Based on its mechanical properties, human vocal fold can be divided into three layers: mucosa plus superficial layer of lamina propria (Reinke's space), ligament, and muscle. The geometry and material properties of these layers determine vocal fold vibratory characteristics. Although the importance of the multilayered structure of vocal fold has long been recognized, the understanding of how the variations of the geometry and material properties of vocal fold layers affect phonation is still very limited. Improving such understanding would benefit both voice treatment and clinical research. For example, it could allow us to predict/estimate the impact of tissue damage, i.e. stiffening of the superficial layers of the vocal fold, and the placement of injected biomaterials. It could also assist the development of engineering vocal fold tissue and prosthesis for replacing damaged tissue. Knowing what geometry and material properties that phonation is most sensitive to could also be valuable for future model creation or model complexity reduction. The PIs propose to utilize a high performance, three-dimensional continuum mechanics based flow-structure interaction model to systematically examine and quantify the effects of geometry and material properties of vocal fold layers on phonation. The study aims to identify the geometry and material properties of vocal fold layers that phonation is most sensitive to, and understand how the variations of these properties affect vocal fold vibration and voice. The long term goal is to establish a direct cause-effect link between vocal fold anatomy (geometry and material properties) and phonation. The two specific aims are as follows: (1) investigate the effects of geometry of vocal fold layers on vibratory dynamics, aerodynamics and sound sources; (2) investigate the effects of material properties of vocal fold layers on vibratory dynamics, aerodynamics and sound sources.